The present invention relates to electrically conductive wires particularly for use in fencing systems used to provide a secure enclosure for livestock, horses, etc.
In the past, it has been known to include electrically conductive wires in fence constructions for the confinement of livestock. Such systems have typically included one or more electrically conductive wires, representative examples of such systems being disclosed in U.S. Pat. Nos. 3,669,413 and 3,223,796. However, bare wire systems such as that disclosed in the 3,669,413 patent are unsatisfactory from the standpoint that they lack aesthetic appeal. Moreover, poor visibility associated with plain or barbed wire fences can lead to painful injury to the animals, and the usually small diameter of such bare wires only exacerbates the potential harm. Improved fencing systems utilizing a single electrically conductive, plastic coated wire in combination with a plurality of vertically spaced plastic webs, and a system using a plurality of vertically spaced electrically conductive, plastic coated wires are disclosed in my copending application Serial No. 008,659, the disclosure of which is incorporated herein by reference.
In non-conductive versions of the plastic coated wire systems described in my above mentioned copending application, the visibility and safety problems are overcome by providing a high tensile strength elongated core wire encased in the relatively thick coating of highly visible, preferably white plastic material. However, in the electrified version, the wires are necessarily made less visible to the livestock or other animals by reason of the manufacturing process by which the wires are made electrically conductive. Specifically, by adding carbon black particles to the plastic composition prior to extrusion over the core wire, the otherwise highly visible plastic sheath material is darkened considerably.
In accordance with the present invention, electrically conductive wires for fencing systems are provided which have the aesthetic appeal of the plastic encased wires disclosed in my prior application along with the desired degree of high visibility, but also have the benefits of electrical conductivity. In accordance with one exemplary embodiment of the present invention, a conductive wire for use in fencing systems is provided which comprises an inner metal conductor wire, a relatively thick intermediate sheath or layer of conductive plastic applied over the conductor wire, and a relatively thin outer sheath of visibility enhanced (preferably white) plastic material applied over the intermediate layer, wherein the outer sheath is sufficiently thin to permit passage of electrical current through the outer sheath.
The core wire is preferably standard electrical wire such as 121/2 gauge, polymetric material, cable, etc., and the intermediate plastic layer or sheath, as well as the thin outer sheath, may be polyvinyl chloride, polypropylene and rubber or other thermoplastic olefin polymers or similar materials.
Various conventional techniques may be employed to encase the core wire within the intermediate, conductive plastic sheath, and thin outer sheath. In accordance with one exemplary embodiment, the intermediate plastic layer or sheath is extruded onto the core wire so that the plastic is fixed to the wire strand, i.e., there is no relative sliding motion therebetween. Extruding plastic coatings or layers onto wire strands is not in itself new, and reference is made to U.S. Pat. No. 4,182,382 which discloses a representative prior art plastic extruding technique.
The thickness of the intermediate plastic coating or sheath is such that the outside diameter of the composite strand and intermediate sheath is preferably from at least about 0.050 inch to about 0.75 inch.
The intermediate plastic layer or sheath is made electrically conductive preferably by the incorporation of carbon black particles to the plastic material prior to extrusion.
In accordance with an exemplary embodiment of the invention, the relatively thin outer sheath is subsequently extruded over the intermediate plastic layer, the thickness of this outer sheath being approximately 0.003 to 0.004 inch so that the final outside diameter of the composite wire is not appreciably greater than the 0.50 to 0.75 inch diameter mentioned above. This outer sheath is thus made thin enough to permit the passage of electrical current from the intermediate conductive sheath through the outer sheath so that animals coming into contact with the wire will receive the desired electrical shock which will cause the animals to remain within the confines of the enclosure. The plastic material which comprises the relatively thin outer sheath comprises, preferably, a highly visible white plastic (or other visible color such as yellow) so as to achieve the benefit of high visibility along with the desired electrical conductivity.
In still another aspect, electrically conductive wires of the type described above may be incorporated into a fencing system including a plurality of vertically spaced wires, or within a system incorporating a single electrically conductive wire in combination with one or more vertically spaced plastic webs, as described in my above identified copending application.
Other objects and advantages of the present invention will become apparent from the detailed description of the drawings which follow.